The prevention of sweetpotato whitefly, Bemisia tabaci (Gennnadius) by combined application an entomopathogenic fungi, Paecilomyces tenuipes pesticide and physical control pesticides was examined under laboratory and greenhouse conditions. In the laboratory, the control effects by the combined application that two pesticides were mixed with under the half concentration of standard usage were higher than single pesticide treatment with standard concentration. Moreover, this effect was confirmed under low relative humidity, 40RH. Improvement of the control effect was confirmed under the greenhouse condition.